The invention relates generally to solid state power sources, and more particularly, to a microwave power source which combines multiple solid state power generating circuits in a central combining cavity.
Research has been conducted towards the goal of maintaining the excellent performance, reliability and durability of solid state microwave power sources while increasing their power output. Prior techiques include combining multiple microwave power sources in a cavity. One technique feeds the combining cavity with the power outputs of a plurality of solid state, negative resistance oscillator circuits which are disposed near the periphery of the cavity. The number of oscillator circuits which can be coupled to the cavity near its periphery is determined by the length of that periphery and the size of the coupling port of the oscillator circuit. Consequently, the amount of output power from the cavity is limited since the number of oscillator circuits contributing to that power is limited.
Various techniques have been developed in attempts to generate higher power levels in a cavity power combiner including increasing the cavity size. However, where the periphery of the cavity is increased to accommodate a larger number of oscillator circuits, oscillation at undesirable higher order modes would be supported with a corresponding dissipation of microwave power and possible instability in operation. Some of these techiques are shown in U.S. Pat. Nos. 4,189,684; 4,172,240 and 4,097,817.
The above techniques purportedly enable the generation of increased microwave power from a solid state type power combiner, however the dissipation of the heat which is also generated by the oscillator circuits, is not satisfactorily addressed. The heat must be dissipated in order to preserve the reliability of the solid state device and where overall size and weight of the power combiner are primary considerations, the heat dissipation equipment must be kept small and light. External fluid cooling systems have been used, however, they are typically bulky and add a significant amount of weight and size to the power combiner. Adding a heat sink to the power combiner also increases weight and size.